Rolamite pushbutton switch



O Unlted States Patent l 13,548,138

[72] Inventor Gilbert A. Van Dine 1,083,412 6/1960 Germany 200/ I59 Winfield Township, Du Page County, Ill. 1,158,085 6/1958 France 200/159 1 1 pp 3 OTHER REFERENCES ggf is: :2 Product Engineer Vol. 38, No. 24, November, 1967,

1 McGraw-Hill Publishers; 39 [73] Assignee Bell Telephone Laboramfies lncorporaed Rolamite: A New De ign Concept (1) by D. F Wilkes; gigf'ffvi October, 1967, Sandia Laboritores Publishers; all Qust title a page included). Group 340 Rolamite: A New Design Concept (ll)" by D. F. Wilkes; 54 R AMITE PUSHBUTTON SWITCH December, I967, Sandia Laboritories Publishers; All (pp. 54, I 1 8 claims, 8 Drawing m 221670, 86, 112, 127, 143, 163,81 170 & 201 included). Group 2 0.8. CI 200 159, [5 1 204/153 Primary Examiner-Robert K. Schaefer s11 lnt.Cl 110111 3/12 vanderhye 501 Field ol'Search 200/52Cap, Ammeys- Guemhe' and Edwin Br Cave 52L. I59, 153, (Inquired) [56] References Cited 3 225 228 l 2 JT PATENTS 3 0 2 ABSTRACT: The principles of a rollerband device are applied 3 419 697 1251968 a an 200/52 to the construction of a pushbutton switch by providing each 3452l75 6/1969 9 of the two roller elements with a respective integral shaft and 3'452309 6/1969 i 1X by providing shaft hearings on the inner surface of a hollow l as pushbutton member. Circuit completion may be effected, al- FOREIGN PATENTS ternatively, by mechanical contacts, by light transmission, 526,230 6/1931 Germany Library capacitively or inductively.

IOI I02 l M I I I I0 III a o I I3 mg PATENTEUUEBISIQYB Y 3,548,138

'OUTPUT 504 602 603 ATTORNEY noLAMrrE rusnnurron swrrcn asc xonouun or THE INVENTION I I.FieldoftheInventionv I I This invention relates to manually. operable electrical 5 substances, contact wear, and unsuitable force versus depression characteristics are some of the problems involved, any one of which may adversely affect either the reliability orthe convenience of switch operation which in turnadversely affects the operation of theassociated equipment.

A typical, conventional and widely used type of pushbutton switch is shown by R. E. Wirshing in US. Pat." No. 2,873,334,

issued on Feb. 10, I959.Considering-thesimplicity of the function performed, it is evident that the structure of switches is undesirably complex. Accordingly, a broad object of the invention isto simplify the'construction of pushbutton switches. I Another object is to enhance the reliability of such switches.

' Inasmuch as keyboards being utilized in the computer and communications fields are increasing in size and complexity,

the rapidity with, which a number of pushbutton switches can be sequentially operated is now a'major consideration in pushbutton design. The speed of operation is in large measure atfected'by the pushbutton feel, which, is primarily determined by the'force versus depression characteristic. In the prior art this consideration has played a minor role, and'has necessarily been compromised or controlled by consideration given to other requirements. Accordingly, a primary object of this invention is to incorporate in a pushbutton switch preselected force versus depression characteristics substantially independent from other design requirements.

, SUMMARY OFTHIZINVENTION The stated objects and related objects are achieved in accordance with the principles of the invention bytuming to account certain features of a relatively new mechanical forcetranslation device commonly termed a roller band" which is also identified'as a Rolamite device. A roller band comprises a pair of roller members with parallel axes in combination with a flexible metal band, such as steel, disposed in an S-configuration separating the rollers and looping around one side of each of the rollers. The assembly is slipped between parallel surfaces and the band ends are pulled into tension and anchored. The device is virtually frictionless and can be rolled from one end of its assembly to the other with very little force. In comparable arrangements of wholly conventional roller bearings or ball bearings, the friction; forces are typically between times and 100 times greater than in the roller band device. A roller band unit can be miniaturized to a remarkable degree, needs no lubrication in service, is inexpensive to, produce, demands no precise tolerances and, is relatively insensitive to dirt. A wide variety of uses has been suggested for various forms of the roller band device, including use as a thermostat, pivot, bearing, speed reducer, snap-action's 'witch, valve, shock absorber, damper, relay and piston. Roller band-devices and various proposed uses thereof are described in the Mechanical Design and Power Transmission portion 'of Product En gineering," Nov. 6,1967, published by McGraw-I-Iilh As indicated above, the general suggestion of adapting the principles of the roller band'to a switch has been made in the prior art. The features of the, invention disclosed herein are directed to specific and unique means for accomplishing the broadly suggested adaptation and more particularly to specific and unique means for adapting a roller band device to the needs of a pushbutton switch.

In accordance with the invention each of two roller elements in a roller band device is formed with respective integral shifis. Bearings for the shafts are provided on opposite interior surfaces of a hollow pushbutton member. An outer fixed casing member provides anchoring points for the spring band and also provides the parallel surfaces which support the rollers. Circuit completion may be effected advantageously by metallic contacts, by controlled light transmission, capacitively or inductively.

I DESCRIPTION or THE'IDRA'WING 7 FIG. 1 taken along the staggered line 2-2;

FIG. 2B is a cross section view of a first alternative bearing detail for the device shown in FIG. 2A;

FIG. 2C is a cross section view of a second alternative bearing detail for the device shown in FIG-2A;

FIG. 3 is a plan view of the band 106 shown in FIG. 1;

FIG. 4 is a partial cross section view of the assembly shown in FIG. 1 wherein circuit completion is effected. by light transmission;

FIG. 5 is a partial cross section view of the. assembly shown in FIG. I wherein circuit completion is effected inductively; and

FIG. 6 is a partial cross section view. of the assembly shown in FIG. I wherein circuit completion is effected capacitively.

DESCRIPTION OF THE EMBODIMENT :the rollers 104 and 105 in an Sconfiguiation. One end 107 of the band 106 is anchored by terminal screw 112, and the opposite end 108 is secured by a tension adjusting screw 109. It will be obvious that a spring or other tensioning device may be substituted for the adjusting screw. Accordingly, both ends of the band 106 are anchored to the casing member. A second terminal screw 113 supports a switch contact l 14, and electrical leads 115 are fixed to the terminal screws I12 and 113.

so. pressing downwardly on the top portion of the pushbutton Operation of the pushbutton switch 101 is effected by 102. In accordance with the invention, the axes of the rollers I04 and 105 are parallel and remain equidistant irrespective of upward or downward travel. As a'consequence the pushbutton 102, being supported by the four shaft ends of the rollers, is constrained from any lateral or tilting motion, and is free to move along in the direction of roller motion. As the rollers I04 and 105 move downwardly togetherwith the pushbutton 102 to which they are afiixed, the end or freeportion 116 of the band 106 is lengthened and the end or free portion 117 of the band 106 is shortened. During operation, the only potentially significant source of friction in the switch is present at the bearing points at which the shafts I10 and I 11 support the pushbutton 102. Such bearing points may readily be designed for minimal friction. Some slight additional friction occurs from the pressure of the rollers 104 and against the spring band 106 and between the band 106 and the inner surfaces of the housing 103. The combination 'of the friction forces indicated, however, is insignificant, and the force-displacement characteristics of the switch are determined almost entirely by the characteristics of the roller band unititself. As is known in the prior art, the band characteristics may be tailored to meet specific needs by cutting holes or slots in the band 106, such as the slot 301 shown in FIG. 3, or by varying the bandwidth or spring constant.

Thus, pushbutton force available for switch operation, as a function of the degree of pushbutton depression, may be precisely controlled in both amount and direction by proper band design. Since pushbutton switches commonly have requirements for a detent, the inherent ability to design the required force reversal at any point in the pushbutton travel is another consideration which makes the device particularly advantageous for use in-such switches.

When the switch shown in FIG. 1 reaches the lower end of its travel, mechanical contact is made between the switch contact 114 and the conductive spring band 106, thus completing a circuit path between the leads 115. The motion of the band at the moment of contact is partially at right angles to the contact 114, producing a wiping action which is known from the prior art to be particularly advantageous for keeping contacts clean.

As shown in FIG. 2A the integral shafts 110 and 111 of the rollers 104 and 105 are supported in corresponding apertures in the sides of the pushbutton 102. Even greater simplicity in fabrication may be achieved by employing dimplelike depressions on the interior surface of the pushbutton 102 to serve as bearing surfaces for the shafts 110 and 111, as shown in FIG. 28. Another alternative bearing arrangement is shown in FIG. 2C.

A wide variety of materials may be employed for the construction of a switch in accordance with the invention. Plastics such as nylon and Teflon are particularly advantageous materials for the rollers and their integral shafts, owing to their low cost, suitability for mass production and their low coefficients of friction. I

I Circuit completion of a switch in accordancewith the invention may be effected by various means as shown, for example,.in FIG. 4 where a light source 401 introduces a beam 402 into the cavity 202 of the housing 103. When the switch 101 is moved to its on position, the light beam 402 is reflected from the highly reflective surface of the band 106 into a .lightconducting optical fiber 403. The light thustransmitted may then be employed to effect circuit completion by, means of a conventional photosensitive device.

Another means of circuit completion. by a switch in accordance with the invention is shown in FIG. 5. Coils 501 and.

502 are positioned within the cavity 202 but theinductive coupling between them is normally insufficient to pass the air ternating current signal from the input leads 503 to the output leads 504. When the switch 101 is operated, however, the roller and band bridges the gap between the pole pieces 503. Provided the band, or both the band and the roller are made of magnetically permeable material, the inductive coupling between the coils increases sufficiently to permit the completion of an inductive path from leads 503 toleads 504.v

FIG. 6 illustrates a means'of circuitcompletion-employingcapacitive coupling. An AC input-is coupled from the input leads 602'to the output leads 603 by means of the capacitive 0 plates 601 in combination with the conductive band 106.

It is to be understood that the embodiment described herein is merely illustrative of the principles of the invention. Narious modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention.

lclaimz, ,1 l. A switch comprising, in combination; l a substantially hollow body portion;

a partially hollow pushbutton member mounted for piston-' like movement within said body portion; a flexible resilient band with each of the; end portions thereof affixedto respective diametrically opposed para]- tegral shaft members; said pushbutton member including first bearing means supported by said shaft members thereby permitting rotational movement of said shaft members; said parallel portions serving as second bearing means for supportingsaid band as. said roller members bearoutwardly against. said band, said roller members being constrained thereby to roll in a linear direction only;

.whereby the force-displacement characteristics of said pushbutton member are determined primarily by the characteristics of said band rather thanby frictional forces; and

electrical circuit means operatively' responsive to a preselected: length of travel of said pushbutton member.

2. Apparatus in accordance with claim '1 wherein said protruding shaft members are integralwrth said roller members.

3. Apparatus in accordance with claim-1 wherein said first bearing means comprises depressions on the inner surfaces of said pushbutton member.

4. Apparatus in accordance with claim 1 wherein said circuit means includes a lightsource directing a light beam into the :lower portion of said body member, said band serving as a reflecting surface for said beam when said band is moved into the path of said beam, and means for conducting said beam when so reflected thereby to complete said circuit.

5. Apparatus in accordance with claim 1 wherein said cir- -cuit means includes first and second pairs of leads, each of a roller band mechanism comprising .a resilient band and a'\ pairof roller members housed substantially within said pushbutton member;

said roller members each including a respective integral shaft member;

first bearing surfaces on the-inner surface of said pushbutton member for supportby said shaft members;

second bearing surfaces onthe inner surface of said body member for supporting said roller members as'they press outwardlyagainst said band,the ends ofsaid band being affixed to said body member; and

means responsive to thezdownwar'd movement of said pushbutton and said roller band mechanism for completing an electrical circuit.

r 7. Apparatus in accordance with claim 6 wherein said first bearing surfaces comprise apertures. in the walls of said body of protruding, in- 

